全文获取类型
收费全文 | 61篇 |
免费 | 2篇 |
专业分类
化学 | 48篇 |
数学 | 2篇 |
物理学 | 13篇 |
出版年
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 6篇 |
2007年 | 1篇 |
2006年 | 5篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有63条查询结果,搜索用时 0 毫秒
11.
12.
A transportable GC x GC instrument is under development for on-site applications that would benefit from the enhanced resolution and powers of detection, which can be achieved by this method. In the present study, a low-resource GC x GC instrument using an electrically heated and liquid-cooled single-stage thermal modulator that requires no cryogenic materials is evaluated. The instrument also uses at-column heating, thus eliminating the need for a convection oven to house the two columns. The stainless-steel modulator tube is coated with PDMS, which can be heated to 350 degrees C for sample injection into the second-dimension column. The modulator is cooled to -30 degrees C by a 100 mL/min flow of PEG by means of a commercial liquid chiller and a small recirculating pump. Resistive heating of the modulator tube is provided by a programmable power supply, which uses a voltage program that results in increasing modulator temperature during an analysis. This, together with more rapid cooling by the use of a liquid cooling medium, results in reduced solute breakthrough following each heating cycle as the modulator cools to a temperature where quantitative trapping resumes. As a result, modulated peak widths at half-height of less than 40 ms are observed. Design and performance details are presented along with chromatograms of gasoline and an essential oil sample. 相似文献
13.
Ostler RB Scully AD Taylor AG Gould IR Smith TA Waite A Phillips D 《Photochemistry and photobiology》2000,71(4):397-404
The results of a study of the effect of pH on the photophysics and photochemistry of di-sulphonated aluminum phthalocyanine (AlPcS2 ) in aqueous solution are presented. The pH dependence of the triplet quantum yield, fluorescence quantum yield, singlet-oxygen quantum yield, triplet lifetime, fluorescence lifetime and apparent dimerization constants is investigated and the results interpreted in terms of the pH dependence of the nature of the axial ligands. Evidence that the aluminum–axial ligand bond strength, rather than dimer binding energy that determines the extent of dimerization is provided by semi-empirical and ab initio calculations. Possible dimer structures obtained using ab initio calculations are discussed. 相似文献
14.
15.
Wang J Even MA Chen X Schmaier AH Waite JH Chen Z 《Journal of the American Chemical Society》2003,125(33):9914-9915
In this Communication, we demonstrate the novel observation that it is feasible to collect amide signals from polymer/protein solution interfaces in situ using sum frequency generation (SFG) vibrational spectroscopy. Such SFG amide signals allow for acquisition of more detailed molecular level information of entire interfacial protein structures. Proteins investigated include bovine serum albumin, mussel protein mefp-2, factor XIIa, and ubiquitin. Our studies indicate that different proteins generate different SFG amide signals at the polystyrene/protein solution interface, showing that they have different interfacial coverage, secondary structure, or orientation. 相似文献
16.
Dr. Yasar Akdogan Dr. Wei Wei Dr. Kuo‐Ying Huang Dr. Yoshiyuki Kageyama Eric W. Danner Dusty R. Miller Nadine R. Martinez Rodriguez Prof. Dr. J. Herbert Waite Prof. Dr. Songi Han 《Angewandte Chemie (International ed. in English)》2014,53(42):11253-11256
Sessile marine mussels must “dry” underwater surfaces before adhering to them. Synthetic adhesives have yet to overcome this fundamental challenge. Previous studies of bioinspired adhesion have largely been performed under applied compressive forces, but such studies are poor predictors of the ability of an adhesive to spontaneously penetrate surface hydration layers. In a force‐free approach to measuring molecular‐level interaction through surface‐water diffusivity, different mussel foot proteins were found to have different abilities to evict hydration layers from surfaces—a necessary step for adsorption and adhesion. It was anticipated that DOPA would mediate dehydration owing to its efficacy in bioinspired wet adhesion. Instead, hydrophobic side chains were found to be a critical component for protein–surface intimacy. This direct measurement of interfacial water dynamics during force‐free adsorptive interactions at solid surfaces offers guidance for the engineering of wet adhesives and coatings. 相似文献
17.
Gel layer formation and hollow fiber membrane filterability of polysaccharide dispersions 总被引:2,自引:0,他引:2
Gel layer formation on the membrane surface during filtration plays a significant role in membrane fouling that, in many instances, controls water production and energy consumption in the treatment of waters and wastewaters. In this study, alginate is selected as a model of the polysaccharides prevalent in wastewaters which, on membrane filtration, may form a gel on the membrane surface which subsequently limits filtrate throughput. We show that over the range of the applied pressures of 11.7–135 kPa considered here, constant pressure ultrafiltration of alginate follows the behavior of cake filtration. The material properties of the alginate are determined by the employment of the previously developed steady-state filtration approach. The consolidation of the gel layer is found to be controlled by the hydraulic flow resistance rather than the rearrangement of particles. Under these conditions, it is valid to apply the derived material properties for the quantification of both constant pressure and constant flux filtration. The gel layer formed from alginate is very compressible and far from uniform over its depth. Within the range of the applied pressures, the gel layer is very porous with a water content of more than 96% but very low Darcy permeability of less than 1 × 10−17 m2. During hollow fiber membrane filtration, the local flux is neither uniform nor constant along the fiber length, resulting in non-uniformity of the growth rate, the average porosity and the thickness of the gel layer. The non-uniformity is most apparent at the start of filtration and then gradually diminishes as the gel layer builds up with ongoing filtration. 相似文献
18.
Marchand DH Croes K Dolan JW Snyder LR Henry RA Kallury KM Waite S Carr PW 《Journal of chromatography. A》2005,1062(1):65-78
As reported previously, five solute-column interactions (hydrophobicity, steric resistance, hydrogen-bond acidity and basicity, ionic interaction) quantitatively describe column selectivity for 163 alkyl-silica, polar-group and cyano columns. In the present study, solute retention and column selectivity for 11 phenyl and 5 fluoro-substituted columns were compared with alkyl-silica columns of similar ligand length. It is concluded that two additional solute-column interactions may be significant in affecting retention and selectivity for the latter columns: (a) dispersion interactions of varying strength as a result of significant differences in bonded-phase polarizability or refractive index and (b) pi-pi interactions in the case of phenyl columns and aromatic solutes. These 16 phenyl and fluoro columns were also characterized in terms of hydrophobicity, steric resistance, hydrogen-bond acidity and basicity, and ionic interaction. 相似文献
19.
We report the results of coupled Hartree-Fock computations for the average polarizability, , and hyperpolarizability, , of CH4, C2H6, C3H6 and C3H8. The Hamiltonian matrices are constructed from an extended CNDO model. Small as well as large basis sets were tested. Agreement with available experimental values is within 13% for and 31% for . 相似文献
20.